The invention concerns an automatic load-dependent braking-force control device for fluid pressure actuated brake systems in motor vehicles or trailers.
Braking-force control devices operable according to a function of vehicle load are known. In such devices, the load-dependent graduation of the braking force becomes effective only after a certain braking pressure has been attained; that is, in the initial stage of a braking operation or during light partial braking, the brake cylinders are subjected to pressure not affected by the load-dependent control function, that is, they are acted upon by non-controlled brake pressure. Only at a higher brake pressure, the magnitude of which is adjustable, is this pressure controlled as a function of load and transmitted in this way to the brake cylinders.
The disadvantage of this known braking-force control device, however, is that, in the precontrol range, that is, the range between initial braking pressure and the braking pressure at which the load-dependent control begins, there is poor graduation since only a small area of the central piston is available as an area of action and reaction.